Artificial tooth



Patented Nov. 13, 1951 UNITED STATES PATENT o1=`l='1c`l =.y

2,574,810 ARTIFICIAL 'roo'rH Earl W. Baumgardner, Watsonville, Calif.' Application April 22, 195o,seria1 No. 157,485

Claims. (Cl. 32-8) My invention relates to artificial teeth; and one of the objects of the invention is the provision of shock-absorbing means in the tooth and denture structure similar in action to the natural tooth in the alveolar socket. Another object of my invention is `the provision of an artificial tooth and denture structure in which the tooth may be replaced without damage or other change in the denture. 1

A further object of my invention is the provision of an artificial tooth having an improved occlusal surface.

In articial teeth and the mounting structures in which they are carried, there are a multiplicity of purely mechanical problems, only a correct solution of which permit the solving of the larger one of practical, successful and satisfactory dentures. From the strictly mechanical viewpoint it is among the objects of my invention to provide a structure in which the parts may be standardized and made by production techniques which insure low cost and interchangeability, so that expensive hand-tooling and replacement expense may be substantially reduced.

' The invention possesses other objects, some of which with the foregoing will be brought out in the following description of the invention. I do not limit myself to the showing made by the said description and the drawings, since I may adopt variant forms of the invention within the scope of the appended claims. y

Referring to the drawings: Fig. l is a sectional view of a tooth and the denture in which it is mounted. The plane of section is in the long axis of the tooth and generally transverse to the main body of the denture. Fig. 2 is a plan view of the tooth shown in Fig. 1, looking toward the occlusal surface. Fig. 3 is a plan View of a cup and casing unit embodying a variant form of my invention. Fig. 4 is a plan View of a tooth embodying still another form of my invention. v

In the replacement of natural teeth by articial ones, the major overall problem is the simulation of the natural tooth mounting and functioning. One of the important elements of the problem is the imitation of the resilient setting of the natural tooth in the alveolar process. I accomplish a similar result by interposing between the denture body and the occlusal surface of the tooth, shock-absorbing means and a flexible mounting which permits the small amount of desired accommodating relative movement of the tooth when chewing. This relieves trauma to the underlying tissue, and in partial dentures or bridgework lessens shock and stress on anchor 2 and abutment teeth. My structure is especially indicated where an artificial denture opposes the natural teeth, since irritation, shock and injury to the latter are largely prevented. My tooth structure has a further worth in that it permits the use of teeth with natural inclined planes which give more grinding surface; and this advantage yis enhanced in one embodiment of my invention by including hard crystalline or metallic elements in the occlusal surface. Means are also provided by which a tooth may be readily removed from the denture and replaced, all without change or injury vto thejdenture or other teeth in it.

In the following detailed description, the word denture isused to designate the base on which the tooth is mounted, and includes plate, partial plate or bridge. In the typical showing of Figure l, such denture 2 is made of a hard acrylic resin, and is shown in section as it would appear below the second bicuspid of the patients right lower jaw, as it is viewed by the dentist. 'Ihe concave recess in the bottom conforms to the alveolar ridge, the engaging surface 3 having been molded thereto in accordance with well known practice.

Molded in the acrylic denture is an anchor plate 4, having downwardly turned edges B, fto give added stiffness to the denture and a firm foundation forthe artificial tooth. The central part of the plate is provided with the upwardly extending bulge 1, pierced with the hole 8 which widens into the recess 9, having a spherical bottom surface I0. When the denture is made, an undercut hol is formed below the anchor plate in register with the recess 9. This hole is later sealed with an acrylic resin plug I2 against a closure plate I3.

As molded, the denture provides a preferably cylindrical recess within the buccal and lingual flanges I4 and I5, the bottom of the recess being formed by the central part of the anchor plate.

Seated in this recess and upon the anchor plate it a cylindrical cushion block I6 of resiliently deformable acrylic resin. The block has a central aperture I1 and extends upwardly around the aperture in a conical plinth, leaving a broad bearing surface I8 adjacent the edges vof the buccal and lingual flanges, and a lesser bearing surface I9 on the top surface of the plinth, The faces of the cushion block thus formed provide the seat for the tooth 2l, the lower end of which is complementary to the block. The tooth is made of hard acrylic resin, porcelain or any suitable material in accordance with known methods.

Means are provided for holding Vthe tooth securelyl on the cushion block and yet permitting a slight movement of the tooth under the stresses imposed by chewing. Fixed in place when the tooth is molded of acrylic resin is a cylindrical casing 22, having the bottom 23 formed with a boss 24. The boss and bottom have a central aperture 26, threaded to receive the endrof the screw 21, the head 28 of which is spherical on the under sideto seat against the spherical bottom I of the anchor plate recess 9. Both the holes 8 and I1 in the anchor plate and cushion block are a trie larger than the screw 21 so that slight movement of the screw on its spherical seat which accompanies movement of the tooth is not damped.

If the tooth is made of porcelain 29, as in Fig. 4, a recess is left in it which is somewhat larger than the casing 22. After ring, the casing is then set in the recess with a thin film 30 of acrylic resin between the two to seal the casing to the porcelain. In Fig. 1 the tooth is assumed to be made of acrylic resin, and it is molded around the casing and in direct contact therewith.

It may be observed at this point that the tooth can be made of solid porcelain, or of solid acrylic resin, with only a plate corresponding to the casing bottom 23 embedded therein; or the tooth can be made of solid metal, in which case no plate is needed, `but instead, the screw is threaded directly into the body of the tooth. In either of these variants which will beobvious from an inspection of Fig. 1, as well as in the form shown in lFigure 1, the tooth is capable of a slight lateral rocking movement on the denture mounting and also of a slight axial movement. These movements occur separately or together in response to pressures applied in chewing or in merely clamping the jaws; and are absorbed andthe shock lessened to a considerable extent by the resilient flexure of the cushion block.

Additional shock-absorbing means are provided 'in the casing 22 to carry and damp strong pressures applied to the tooth in an axial direction. The casing which is preferably cylindrical, carries in its upper part a closely tting butV slidable cup or shell 3|, containing a lter of porcelain or other suitable material 32 which is L shaped on its exposed face 33 to provide the central and main portion of the grinding surface of the tooth. The surrounding portion or margin 34 of the tooth is no heavier than is necessary for strength, so that the cup may be as large as possible. For this reason the casing and cup may sometimes be elliptical instead of cylindrical, when the tooth is materially thicker in one direction than another, as is the case with molars.

An elliptical cup such as shown in Figure 3 will not turn in the casing, but with a cylindrical cup it'is necessary to provide means for preventing rotation of the cup which would of course effect 'an objectionable change in the occlusal planes. This is most readily done by threading a pin 35 through the casing wall to engage in a slot 36 in the flange 31 extending downwardly from the bottom edge of the cup.

A heavy spring 38 is interposed between the bottom of the cup'and the bottom of the housing to retain the occlusal surface of the central portion of the tooth normally hush with the marginal portion. The spring requiring a compressive force of the order of ten to twenty-five pounds p. s. i. does not permit inward sliding of the cup under ordinary stresses, but does allow such movement to absorb an unusually heavy shock.

Means are provided for locking the cup in the casing and fixing limits of axial movement of the cup. Seated in an annular groove 39, formed in the thickened bottom 4I of the cup is a at, resilient, split locking ring 42. The locking ring normally expandsinto the annular groove 43 on the inside of the casing, and the parts are so proportioned that with the ring held tightly against the upper rim of the groove by the spring pressure on the bottom of the cup, the occlusal surfaces are properly aligned. The vertical Width of the groove 43 minus the thickness of the ring is of course the measure of maximum axial movement of the cup in the casing.

In order to render the joint between cup and casing as nearly tight as possible against leakage of moisture, spring ring sealing means comprising piston rings Y44 and 45 are interposed between the two, closely adjacent the occlusal surface-of the tooth. Each ring is split, but so formed that when the ends touch, the ring snugly embraces the cup surface. Thus each ring may expand very slightly into the annular groove in the casing in which it also ts snugly. The lower edge 46 of the cup i'lange 31 may be slightly beveled to facilitate entry of the cup into the casing.

The parts are easily assembled. It will be assumed that the pin 35 has been set in the casing, and the casing molded in place in the tooth. The rings 44 and 45 are placed in their annular grooves and the cup started in. The lock ring 42 is then compressed fully into its groove by the ngers or a suitable clamping tool, and the cup pressed down into the casing and turned as necessary to engage the pin 35 in the slotted flange. A short additional inward movement then allows the compressed ring to expand into the groove 43 to lock the parts together. Since the cup ts the casing very closely, the imprisoned air escapes through the apertured bottom of case and tooth. The tooth may now be seated on the cushion block and the screw 21 turned to eiect the desired compression oi' the block'which of course is closely related to the amount of permitted tooth movement. Loosening of the adjusting screw 21 is avoided by making the threaded engagement of the screw with the boss' 24 both long and tight.

'By standardizing the necessary parts, the tooth is made replaceable in the event of injury or needed change without alteration in the remaining portions of the denture. The plug l2 and cover plate I3 are taken out to give access to the screw. Removal of the screw allows the tooth to be removed from its seat in the cushion block. It may then be replaced by a wholly new tooth assembly.

The occlusal surface of the tooth may be improved by the incorporation therein of hard crystalline material such as 'natural or synthetic crystals, or of suitable hard metal. For example, in the occlusal surface of the tooth shown in Figures 1 and 2 a crystal'48 of aluminum silicate is shaped to the cup and held by the acrylic resin 32 which lls the remainder of the cup. In Figure 3 narrow bands 49 of hard metal such as stainless steel are set in the resin 5| to improve the grinding surface.

I claim:

1. An artificial tooth, comprising a tooth body.

a casing in the body, a cup slidably disposed in the casing, resilient means t'o resist movement of the cup in the casing, and a ller in the cup forming a portion of the grinding surface of the tooth.

2. An artificial tooth, comprising a tooth body, a casing in the body, a cup slidably disposed in the casing, resilient means to resist movement of the cup in the casing, a ller in the cup forming a portion of the grinding surface of the tooth. and a plate of material harder than the filler embedded edgewise in the filler and having an edge ililcstantially iiush with the occlusal face of the 3. An artificial tooth, comprising a tooth body, a casing in the body, a cup slidably disposed in the casing, resilient means to resist inward movement of the cup in the casing, positive stop means to limit outward and inward movement of the cup in the casing, and a iiller in the cup forming a portion of the grinding surface of the tooth.

4. A dental structure comprising a denture, an anchor plate embedded in the denture, a cushion block on the anchor plate and having a centrally located aperture extending upwardly therethrough, a tooth body on the cushion block, a casing in the body, said tooth body having an aperture in alignment with the block aperture and extending from the block to the casing, a link engaging the anchor plate and adjustably secured to the casing, said link extending through said aligned apertures and being smaller in lateral dimension than the apertures, a cup slidably disposed in the casing, a spring interposed between the cup and the casing, positive stop means to limit inward and outward movement of the cup, and a filler in the cup forming the major portion of the grinding surface of the tooth.

5. A dental structure comprising a denture, an anchor plate embedded in the denture, a cushion block on the anchor plate and having a centrally located aperture extending upwardly therethrough, a tooth body on the cushion block, a casing in the body, said tooth body having an aperture in alignment with the block aperture and extending from the block to the casing, a link engaging the anchor plate and adjustably secured to the casing, said link extending through said aligned apertures and being smaller in lateral dimension than the apertures, a cup slidably disposed in the casing, a spring interposed between the cup and the casing, positive stop means to' limit inward and outward movement of the cup, means for preventing turning of the cup in the casing, sealing rings in the casing and resiliently embracing the cup, and a filler in the cup forming the major portion of the grinding surface of the tooth.

EARL W. BAUMGARDNER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,105,476 Withycombe July 28, 1914 1,665,154 Withycombe Apr. 3, 1928 2,397,407 Butler Mar. 26, 1946 

